The present invention relates to a label feeder unit and to a method of feeding labels in a packer machine for tobacco products.
In particular, the invention finds application in the art field of devices for dispensing revenue stamps, coupons or tamper-evident seals, and of units for picking up and transferring such items to equipment by which they are affixed or applied to packets containing tobacco products.
In conventional machines for applying labels to packets containing tobacco products, the labels are fed to a pick-up and transfer unit by which they will be gummed and then affixed to the packets.
During the step of feeding the labels to the pick-up and transfer unit, the labels are arranged in one or more ordered stacks, each comprising a plurality of labels placed one on top of another. The labels therefore combine to form a single compact block.
Machines of prior art type for applying labels to packets of tobacco products are equipped with arms supporting the stack of labels, and serving also to establish a feed path along which the labels are advanced. The stack is subjected to a pushing force, directed toward the pick-up unit, so that the labels remain compacted together.
The pressure applied thus to the stack of labels can be generated by simple force of gravity, in the case of a vertical machine, or by push rods in the case of a horizontal machine; at all events, a force is directed through the stack, impinging ultimately on restraints afforded by the ends of the arms aforementioned and facing the pick-up unit.
The function of the restraints is to hold the labels in a predetermined position when taken up from the stack, in such a way as to facilitate the step by which the single labels are picked up.
It has been found, during the operation of conventional machines, that the step of picking up the labels can be problematic.
In effect, a degree of adhesion is created between the stacked labels, due mainly to the force applied at the top or rear of the stack to keep it compact, which works in opposition to the pick-up action.
The extent of the adhesion aforementioned is also difficult to predict, since the force applied to the stack of labels is dependent (especially in vertical machines) on the number of labels remaining in the stack as each successive pick-up is completed.
In addition, the force applied to the compacted labels induces an elastic deformation of the stack, in measure proportional to the number of labels making up the stack at any given moment.
Consequently, it happens in certain circumstances that no label will be picked up, or that two or more labels are picked up at once.
The drawback in question is betrayed particularly by label feeder units in cigarette packers of the latest generation, where labels must be taken from the stack and transferred at rates of up to a thousand per minute.
Accordingly, the object of the present invention is to provide a unit and a method for feeding labels in a packer machine for tobacco products, such as will be unaffected by the drawbacks mentioned above.
One object of the invention, in particular, is to provide a unit and a method for feeding labels in a packer machine for tobacco products, designed to allow a correct and systematic release of the single labels from the dispensing device to the pick-up and transfer unit.
A further object of the invention is to provide a unit and a method for feeding labels in a packer machine for tobacco products, by which labels can be transferred correctly in high numbers per unit of time.